System and method for providing reliable transmission in a buffered memory system

Abstract

The present invention provides a system and method for providing reliable transmission in a buffered memory system. The system includes memory devices, a memory controller, data buffers, an address/command buffer, and a clock circuit. The memory controller sends data, address information, status information and command information, to the memory devices and receives data from the memory devices. The buffers interconnect the memory devices and the memory controller. The clock circuit is embedded in the addr/cmd buffer. The clock circuit takes an input clock and outputs an output clock to the data buffers and/or the memory devices to control clock-skew to the data buffers and/or the memory devices.

What is claimed is:  
     
       1. A memory system, comprising: 
       at least one memory device to store data;  
       a memory controller, to control the at least one memory device, that sends data, address information, and command information to the at least one memory device, and receives data from the at least one memory device;  
       at least one data buffer, located externally from the at least one memory device and the memory controller, interconnecting the at least one memory device and the memory controller;  
       an address and command buffer (addr/cmd buffer), located externally from the at least one memory device and the memory controller, interconnecting the at least one memory device and the memory controller; and  
       a clock circuit embedded in the addr/cmd buffer, wherein the clock circuit takes an input clock and outputs an output clock to the at least one data buffer to control clock-skew to the at least one data buffer.  
     
     
       2. The memory system of  claim 1 , wherein the clock circuit embedded includes a delay locked loop (DLL). 
     
     
       3. The memory system of  claim 1 , wherein the clock circuit embedded includes a phase locked loop (PLL). 
     
     
       4. The memory system of  claim 1 , wherein the clock circuit embedded includes a delay chain. 
     
     
       5. The memory system of  claim 1 , wherein the at least one memory device is a dynamic random access memory. 
     
     
       6. The memory system of  claim 1 , wherein the at least one memory device and the buffer are housed within a memory module. 
     
     
       7. The memory system of  claim 1 , wherein the buffer resides on a motherboard of a computer system and the at least one memory device is housed within a memory module. 
     
     
       8. A buffering device interconnecting a memory controller and a memory device, comprising: 
       at least one data buffer located externally from the memory device and the memory controller, wherein the memory controller controls the memory device;  
       an address and command buffer (addr/cmd buffer) located externally from the memory device and the memory controller to facilitate transfer of command information and address information from the memory controller to the memory device; and  
       a clock circuit embedded in the addr/cmd buffer, wherein the clock circuit takes an input clock and provides an output clock to the at least one data buffer to control clock-skew to the at least one data buffer.  
     
     
       9. The buffering device of  claim 8 , wherein the clock circuit also provides the output clock to the memory device to control clock-skew to the memory device. 
     
     
       10. The buffering device of  claim 8 , further comprising a clock driver for driving the output clock to the at least one data buffer. 
     
     
       11. The buffering device of  claim 8 , wherein the clock circuit includes a delay locked loop (DLL). 
     
     
       12. The memory system of  claim 8 , wherein the clock circuit includes a phase locked loop (PLL). 
     
     
       13. The memory system of  claim 8  wherein the clock circuit includes a delay chain. 
     
     
       14. A method of operating a memory system including a memory controller, a memory device, a data buffer, and an address and command buffer (addr/cmd buffer), the method comprising: 
       transmitting data from the memory controller to the memory device via the data buffer, or from the memory device to the memory controller via the data buffer, wherein the data buffer is located externally from the memory device and the memory controller, and the memory controller controls the memory device;  
       transmitting address information and command information from the memory controller to the memory device via the addr/cmd buffer, wherein the addr/cmd buffer is located externally from the memory device and the memory controller;  
       receiving an input clock by a clock circuit embedded in the addr/cmd buffer;  
       generating a first output clock by the clock circuit embedded in the addr/cmd buffer based on the input clock; and  
       providing the first output clock from the clock circuit embedded in the addr/cmd buffer to the data buffer.  
     
     
       15. The method of  claim 14 , the method further comprising 
       generating a second output clock in the addr/cmd buffer based on the input clock;  
       outputting the output clock from the addr/cmd buffer to the memory device.  
     
     
       16. The method of  claim 15 , wherein the first output clock and the second output clock are identical in frequency and phase. 
     
     
       17. The method of  claim 14 , wherein the first output clock is generated by a delay locked loop (DLL) embedded in one of the at least one data buffer and the addr/cmd buffer. 
     
     
       18. The method of  claim 14 , wherein the first output clock is generated by a phase locked loop (PLL) embedded in one of the at least one data buffer and the addr/cmd buffer. 
     
     
       19. The method of  claim 14 , wherein the first output clock is generated by a delay chain embedded in one of the at least one data buffer and the addr/cmd buffer.